1. Field of the Invention
The invention relates to an apparatus comprising a housing having a first housing wall provided with sound transmission aperatures; a printed circuit board accommodated in the housing and extending substantially parallel to the first housing wall; an electroacoustic transducer having a front and a rear; holding means connected to the printed circuit board and to the transducer, said holding means securing the transducer to the printed circuit board such that the front of the transducer faces the first housing wall in the area of the sound transmission apertures; and sealing means arranged between the first housing wall and the transducer, said sealing means achieving a nominal isolation between the front and the rear of the transducer.
2. Description of the Related Art
Such an apparatus is known as a commercially available mobile telephone in a plurality of variants. In the known apparatus, the holding means is formed by a pot-shaped holder which is fixedly connected to the printed circuit board and has a pot bottom wall adjoining the printed circuit board and intermediate contacts in the area of the pot bottom wall, these intermediate contacts being in contacting engagement with terminal contacts of the transducer and with mating contacts on the printed circuit board. The pot-shaped holder has latching hooks which project in a direction from the pot bottom surface to the first housing wall and have latching noses at their free ends, these latching noses engaging over the transducer in order to retain the transducer and which, depending on the prevailing tolerance conditions, either lie on the first housing wall and, in the case of certain unfavorable tolerance conditions, cause the printed circuit board to be urged away from the first housing wall, which is undesirable, and, in the case of other unfavorable tolerance conditions, do not lie on the first housing wall, which would result in undesirable air gaps if no separate sealing means had been provided, this sealing means precluding the formation of such air gaps and filling up the tangential clearances between the pot-shaped holder and the first housing wall left between the latching hooks. Thus, in the known apparatus, the mounting conditions are tolerance-dependent to a considerable extent and require a comparatively large amount of work in order to achieve a nominal isolation desired between the front and the rear of the transducer. This results in a comparatively large amount of work and, as a result, comparatively high cost.
It is an object of the invention to preclude the problems mentioned hereinbefore and to provide an improved apparatus in a simple manner and by simple means.
In order to achieve the afore-mentioned object, according to the invention, an apparatus as defined in the opening paragraph, is characterized in that the holding means is mounted so as to be movable with respect to the printed circuit board parallel to a direction which extends transversely to the printed circuit board, and the apparatus further comprises spring means for urging the holding means towards the first housing wall under spring load, the holding means being held against the first housing wall with the aid of the spring means, wherein the holding means, at the same time, forms the sealing means.
By providing the characteristic features in accordance with the invention, it is achieved, in a particularly simple manner and by very simple means, that, firstly, an electroacoustic transducer is mounted securely to the printed circuit board of an apparatus in accordance with the invention and, secondly, always a correct nominal isolation between the front and the rear of the transducer is achieved with the aid of the holding means which is present anyway and which is in addition, used as sealing means, thereby always guaranteeing a correct and reproducible acoustic behavior and, thirdly, the means required for this purpose entail hardly any additional cost.
In an apparatus in accordance with the invention, separate spring means may be provided. However, it has proven to be advantageous when, in addition, the spring means is formed by two resilient terminal contacts of the transducer, which resiliently engage with two mating contacts on the printed circuit board, because the resilient terminal contacts of a transducer, which are present anyway, are thus utilized at the same time as spring means.
In an apparatus in accordance with the invention, it has proven to be particularly advantageous when, in addition, the holding means has at least two latching hooks which, extend through the printed circuit board and which have latching noses which engage behind the printed circuit board, because this guarantees a particularly simple mounting and securing of the holding means together with the transducer onto the printed circuit board as well as an easy removal.
In an apparatus in accordance with the invention, the transducer may be connected to the holding means, for example, with the aid of an adhesive joint. However, it has proven to be advantageous when, in addition, the holding means has further latching means for securing the transducer to the holding means, because this enables the transducer to be mounted simply in the holding means and it also enables the transducer to be removed in a simple manner, for example in order to replace the transducer.
The holding means may have various constructions. However, in practice, it has proven to be particularly advantageous when, in addition, the holding means has an upper wall which extends parallel to the first housing wall and has at least one passage for the transmission of sound, the upper wall being adapted to abut against the first housing wall, and forming the sealing means. Such a construction has proved to be advantageous both as regards its simplicity and as regards an optimum isolation between the front and the rear of a transducer of an apparatus in accordance with the invention.
In an apparatus in accordance with the invention including a holding means having an upper wall, it has further proven to be advantageous when, in addition, the upper wall has a plurality of passages for the transmission of sound, the passages being adapted to influence the sound pressure versus frequency response obtainable by means of the transducer, because the holding means with its upper wall is then additionally used for influencing the sound pressure versus frequency response.
In an apparatus in accordance with the invention, it has further proven to be advantageous when, in addition, the upper wall of the holding means forms a part of a holder cap forming the holding means, and the circumferential boundary of the holder cap is formed by the latching hooks and the latching means, because this results in a holding means which guarantees a high degree of protection for the transducer.
The above-mentioned as well as further aspects of the invention will become apparent from the two examples of embodiments described hereinafter and will be elucidated with reference to these examples.